Disable charge pump on Knight of tone

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falcon75
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Post by falcon75 »

Hello Pedal Builders,

I have build a Knight of Tone from PCB Guitar Mania which plays very well. Now the building docs https://pcbguitarmania.com/wp-content/u ... g-Docs.pdf recommend to try it without the Charge Pump if using it with a lot of overdrive.
The doc says there is a graphic which shows howto bypass the charge pump.
Unfortunately I‘m not able to find the required information or graphic.

Looking at the schematic, I’m wondering if I simply need to remove IC3 and that‘s it. Can somebody confirm that?

If I want to have it switchable how can I do this?

Thanks for your help and feedback.
Last edited by falcon75 on 17 Oct 2022, 18:26, edited 1 time in total.

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mauman
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Post by mauman »

Remove IC3 (charge pump). Remove D14 and D15 and replace them with straps, or leave them in and strap around them. The 9V input will then become your V+. You won't need C11, C12 or C13 but it won't hurt to leave them in if they're already installed.

The best way to make it switchable is to move the DC protection and charge pump circuit to a separate vero board, then run the 18V vero output and 9V to lugs 1 and 3 of a SPDT, with lug 2 of the SPDT to the +9V input of the PCB. If you're interested let me know and I can post a diagram.

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Manfred
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Post by Manfred »

If you disconnect pin 4 of the LT1044 from ground it should no longer be activated, so switching would be possible, try it.
A simple possibility would be to use a 5V power supply.

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Post by falcon75 »

Thanks @mauman @Manfred,

I will give it a try.

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BILBO15
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Post by BILBO15 »

Hello

I have bought a knight of tone replica but i have an issue with it.

When i put the drive on 75/100 on one side, there is a rather loud hum coming out of the pedal. It does the thing on both sides and on the 3 modes (od, disto, boost). It becomes very disturbing when the both sides are switched on.

Is it normal or do you think there is an issue that i could fix easily?

I dont think it s due to my power supply because i have 0 problem on other pedals.

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Post by BILBO15 »

Manfred wrote: 17 Oct 2022, 01:15 If you disconnect pin 4 of the LT1044 from ground it should no longer be activated, so switching would be possible, try it.
A simple possibility would be to use a 5V power supply.
I have a power supply that can adapt the voltage. So if i run the pedal on 5v or 6v with no modification inside, it should fix the hum?

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Manfred
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Post by Manfred »

When i put the drive on 75/100 on one side, there is a rather loud hum coming out of the pedal. It does the thing on both sides and on the 3 modes (od, disto, boost). It becomes very disturbing when the both sides are switched on.
Does the hum occur with or without input signal ?
Is the noise humming with the line frequency or does it sound like a different frequency ?

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BILBO15
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Post by BILBO15 »

No hum when pedal is not switched on
Hum happens when pedal is switched on and no guitar is plugged and same when plugged (maybe different sound but not very different)
Hum is not linked to other pedal cause it happens even when alone in the pedalboard
I tried with 6v power and it doesnt change anything

The hum is in the background so not linked to the line frequency i think. The hum gets louder with the drive or volume of pedal and more trebly with the tone.

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Post by Manfred »

BILBO15 wrote: 07 Sep 2023, 08:59 No hum when pedal is not switched on
Hum happens when pedal is switched on and no guitar is plugged and same when plugged (maybe different sound but not very different)
Hum is not linked to other pedal cause it happens even when alone in the pedalboard
I tried with 6v power and it doesnt change anything

The hum is in the background so not linked to the line frequency i think. The hum gets louder with the drive or volume of pedal and more trebly with the tone.
This could be oscillation in the circuit.
Short-circuit the input to ground and see what happens.

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Post by BILBO15 »

Manfred wrote: 07 Sep 2023, 18:55
BILBO15 wrote: 07 Sep 2023, 08:59 No hum when pedal is not switched on
Hum happens when pedal is switched on and no guitar is plugged and same when plugged (maybe different sound but not very different)
Hum is not linked to other pedal cause it happens even when alone in the pedalboard
I tried with 6v power and it doesnt change anything

The hum is in the background so not linked to the line frequency i think. The hum gets louder with the drive or volume of pedal and more trebly with the tone.
This could be oscillation in the circuit.
Short-circuit the input to ground and see what happens.
You mean moving the link going out of the jack to the ground?

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Manfred
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Post by Manfred »

Input short.jpg
Input short.2 .jpg
Input short.2 .jpg (15.12 KiB) Viewed 2457 times

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Post by BILBO15 »

I tried to short circuit the input and the sound is here

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Post by BILBO15 »

https://streamable.com/886ggh?src=player-page-share

Video of the sound.

It is not nvery noticeable but the sound happens too when only one side of the pedal is engaged, just louder with both sides

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Manfred
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Post by Manfred »

This sounds like noise.
The cause could be bad noise OP-amps , where did you buy them?
I see they are mounted the OP-amps sockets, so you can replace them with low noise types like NE5532 to see if the noise intensity goes down.
Do you have an oscilloscope?

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BILBO15
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Post by BILBO15 »

I bought the pedal like this. So no idea where they Come from.

The more important would be to change the 2 identical op amps or the central one?

I luckily have 2 ne5532p. Would it be a good swap?

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Post by Manfred »

BILBO15 wrote: 09 Sep 2023, 09:16 I bought the pedal like this. So no idea where they Come from.

The more important would be to change the 2 identical op amps or the central one?

I luckily have 2 ne5532p. Would it be a good swap?
This is just a test to see if the noise is gone or becomes less intesive using the NE5532s
If it would be better, it is then the question whether the sound changes depending on the type of OP amp.

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Post by BILBO15 »

I swapped with the 2 ne5532p and the noise is still there. When everything at max, i can now hear the radio with the input short circuit to ground!!!

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Post by Manfred »

BILBO15 wrote: 09 Sep 2023, 09:45 I swapped with the 2 ne5532p and the noise is still there. When everything at max, i can now hear the radio with the input short circuit to ground!!!
Solder a 22pF capacitor in parallel to R1 and RB1 and see if the radio reception is gone.
Otherwise it could also be a wiring problem.
Please give us detailed shots.

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Post by Manfred »

Did you make any progress in troubleshooting?

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Post by falcon75 »

falcon75 wrote: 17 Oct 2022, 18:23 Thanks @mauman @Manfred,

I will give it a try.
Just to confirm: disconnecting Pin4 from ground just works fine. I also bypassed the diodes, but I don't think this is mandatory.

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